Only two minor changes happened into the data format of a scan containing a single spectra. The data is stored as a header (divided in independent sections) and the data. We have added: 1) the three parameters associated to the descriptive coordinate system (2 parameters for the system center + the system position angle) to be able to go from this descriptive coordinate system to a standard (e.g. equatorial) coordinate system and 2) a subscan number. This subscan number is foreseen to always be greater than 1. There is one exception: when CLASS90 read data in old format, the subscan number is zero and a warning is issued.